Planing hull



Dec. 22, 1964 J wYNNE 3,162,167

PLANING HULL Filed July 29, 1963 INVENTOR. JAMES R. WYNNE W rm ATTORNEYS United States Patent Ofifice 3,l62,lb? Patented Dec. 22, 1964 3,162,167 PLANDIG HULL James R. Wynne, Miami, Fla, assignor to (Jlirnax Marine Corporation, Sarasota, Fla, a corporation of Florida Filed July 29, E63, Ser. No. $8,369 3 filaims. (Cl. lid-66.5)

This invention pertains to speedboat hulls of the planing type and more particularly to improvements in planing hulls of the type comprising a V bottom provided with a plurality of longitudinal strakes, and wherein the strakes include downwardly facing planing surfaces.

Recent years have seen the introduction of V bottom hulls in speedboats which are provided with longitudinal strakes, and such strakes are provided in successful hulls of the so-called Moppie or Hunt type. These hulls have the desirable easy-riding qualities and stability and safety in rough water characteristic of V bottom hulls, coupled with the low resistance and substantially flat bottomed speedboats. The Moppie or Hunt type hull includes a fiaired ship-shape prow smoothly contoured into a moderate V bottom extending from the prow throughout the length of the boat to the stern transom, typically includes a hard chine, and includes a plurality of prominent longitudinal strakes extending from the prow portion of the hull through at least a major length of the waist portion of the hull. Some or all of the strakes may extend aftwardly to the transom, but it has been found desirable particularly in smaller hulls of, for example, less than about 25 feet overall length which are intended for higher speeds, for example, in excess of 25 to 30 knots, to terminate one or more of the lowermost or innermost strakes, those nearer the keel, several feet forward of the transom, thereby to reduce the total wetted surface of the portion of the hull which is subjected, during high speed operation, to the maximum water pressure. It is desirable, however, that the strakes adjacent the chines extend to, or substantially to, the transom, since the chines and the outer portions of the bottom adjacent the chines are out of water during steering maneuvers, when the hull is sharply heeled, when a wave crest may momentarily wet the chines, or when the hull is violently pitching. During operation at less than planing speeds, the chine at the transom is at approximately water level.

It has also been found satisfactory to eliminate entirely the lowermost strakes of the earlier models of Hunt or Moppie hulls. The V bottom hulls which are herein referred to as Hunt or Moppie hulls may comprise as few as two strakes (on each side of the keel), one of which may constitute a spray rail and may be coincident with the chine, and the other of which is a well defined strake located below and inwardly of the one strake and spaced therefrom by a distance equal to a small fraction of the beam dimension of the hull, for example, by about one-tenth of the beam dimension.

An object of this invention is to improve hulls of the type comprising longitudinal strakes. A more specific object of the invention is to improve the low speed operating characteristics of hulls of the type comprising longitudinal strakes, such as, specifically, hulls of the Moppie or Hunt type.

Another specific object of the invention is to provide improved means in a hull of the type having longitudinal strakes, such as a lvloppie or Hunt type hull, for causing the hull when accelerating more rapidly and at lower speed to assume the desired planing attitude, and to cause the hull to starting planing more rapidly and at lower speed.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a perspective View of a complete speedboat embodying the invention, the boat being shown in operation;

FIGURE 2 is a side elevation of the boat of FIGURE 1, on a slightly enlarged scale; and

FIGURE 3 is a stern elevation of the boat on a further enlarged scale.

A hull of the Moppie or Hunt type as described above modified in accord with this invention is shown in the drawings. FIGURE 1 shows a complete speedboat 1 in operation, of which the hull 2 is of the Moppie or l-Iunt type comprising a flaring prow 3 terminating forwardly in a pointed stem 4 and having a plurality of longitudinal strakes including an upper and outermost strake 5 which is in this embodiment coincident with and constitutes the hard chine of the hull, and which serves as and is sometimes designated as a spray rail, a next occurring intermediate strake 6 which in this embodiment joins the chine and terminates at a forward end portion 7 at approximately the forward end of what may be considered the waist portion 35 of the hull, or the aftward end of the prow portion 3. A lower intermediate strake 8 extends forwardly to the stem 4 and, while the uppermost strake 5 and the adjacent and next occurring strake 6 extend aft to the stern 9, both the lower intermediate and lowermost strakes 8 and 10 terminate, as best seen in FIGURE 2, forwardly of the stern at 11 and 12, respectively. The boat is seen to be steered and powered by an inboard-outboard drive unit including outboard assembly 13 connected centrally of the stern transom 14 and comprising propeller 15. Such a unit is described in US. Patent No. 3,006,311, issued October 31, 1961, entitled Boat Steering Means Including a Swingable and Tiltable Outboard Unit. This outboard assembly has been omitted from the view of FIGURE 3 for clarity.

The high and low speed waterlines of the hull are represented by the respective broken lines 16 and 17 in FIG- URE 2. It will be seen that, at low speeds, the transom is submerged up to substantially the chine or outermost strake, whereas at planing speeds, the chine and first intermediate strake are out of water for their full lengths to the stern.

The shapes of the strakes and outer hull surface are best seen in FIGURE 3. Strakes 6, 8 and Ill comprise downwardly facing lower planing surfaces 18, 19 and 26, respectively, extending substantially horizontally outwardly from the smooth hull outer surface and smoothly faired therefrom, and the lower surface of each strake terminates outwardly in an edge, such as edge 21 of strake It A generally upright surface, such as surface 22 of strake Ill, joins the planing surface of the strake along the strake edge 21 and extends upwardly and fairs smoothly into the hull surface. The upper strake 5 defining the chine includes a lower planing surface 23 shown in broken lines in FIGURE 3, an outer edge 24, and an upwardly extending outwardly facing surface 25 which extends upwardly to and joins the side 26 of the hull.

The distance along the hull surface between adjacent strakes is preferably equal to between one and two times the distance subtended by a strake. More particularly, the distance between the line 27 along which surface 22 joins the hull surface and line 28 along which surface 19 joins the hull surface is equal to between one and two times the distance between line 27 and a line 29 along which surface 18 of strake ill meets the surface of the hull. Each strake is similarly spaced from the next occurring strake on each side of the keel 30. While 3 only one side of the hull is described, it. will be apparent that the hull is symmetrical about the keel.

The specific function of planing surface 20 of strake 6 is, particularly at high speed, to direct water rising along the hull surface generally horizontally outwardly. At lower speeds, or whenever it is in the water, spray rail or strake serves a similar function.

The lower strakes 8 and 10 function also in this manner, but it will be apparent to those skilled in the art that this invention does not depend upon the presence of strakes 8 and 10. I

A theory of operation of hulls to which this invention pertains is thus that with the V bottom water tends to rise along the bottom surface coming in contact with the planing surface 2% of strake 6, that the upwardly moving water meeting this surface provides upward force thereon tending to lift the hull, and that this surface directs the water outwardly away from the hull surface thereby reducing the pressure of water against the portions of the hull surface above the planing surface, or, ideally, resulting in no contact of water with the hull above surface 20. The effect increases with speed, and at low speed water flows up the hull to the planing surface 23 of the uppermost strake 5.

This invention is particularly related to a hull having an outer strake or spray rail 5 which is at least for a part of its length adjacent the stern at or a little below water level when the hull is at rest and at low speed, but which is completely out ofcompacted water at high speed, and having an adjacent strake inwardly of and below such outer strake, which such adjacent strake is below Water level for at least a part of its length adjacent the stern at rest and at low speed, but which is not below the level of hard water at high speed, and which may be substantially at the level of hard water at high speed. It will be understood that this explanation assumes a substantially even keel position for the hull and generally smooth water. By compacted water it is intended to mean that water which by dynamic reaction supports the hull, as opposed to air-ladened water such as spray.

Accordingly to the invention, the curve of the hull is discontinuous near the stern between a pair of strakes 5 and 6 of which the lower strake 6 is at or near water level during high speed operation but, at the stern, is below water level during low speed operation. The hull, in other words, has a shape following along a smooth curve longitudinally of the hull, between strakes 5 and 6 but near the stern this shape changes abruptly and the longitudinal shape aftward from the discontinuity departs from a continuation of the curve. As seen in the drawings, a discontinuous hull surface portion 31 extends at a small angle outwardly from the hull surface from a meeting line or area 32 toward the stern. The discontinuous portion is, as will be seen, disposed entirely between strakes S and 6 and, at the stern or transom, is sub stantially even with the outer edges of these strakes. The hull portion 31, in a seventeen or eighteen foot boat, may have a length of about eighteen inches as measured between the stern and a line 32, where portion 31 meets and is faired into the hull surface portion 33. This surface 33 is represented in broken lines in FIGURE 3. The aftward end of portion 31 at transom 14 may be spaced outwardly from the normalhull surface 33 by approximately one inch. The angle between the outer surface of portion 31 and the hull surface portion 33 is preferably about three degrees but may vary between about two and about six degrees, being nearer two degrees for a longer such surface portion 31 and nearer six degrees for a shorter surface portion 31. The surface portion meets and fairs into the upwardly extending outwardly facing surface 34 of strake 6 and into the downward surface 23 of strake 5. The length of portion 31 may vary, but if this port-ion is less than about one-twentieth of the length of the boat, it will crea e unnecessary drag and if it is longer than about one-fifth, it becomes less effective to perform its desired function.

It will be noted that the hull portion 31 lies for the most part between the high speed and low speed water lines 16 and 17. During low speed operation, water which contacts portion 31 tends to lift the stern of the boat and this effect is more pronounced during rapid acceleration when the thrust of the propeller has the tendency to bury the stern. As the hull reaches planing speed and lifts in the water, the portion 31 is raised completely out of compacted water and thus does not constitute an appreciable drag, although, of course, during turns it may be more or less buried, and it may be contacted by spray, or by wave crests. During abrupt turns it has been found that the action of the buried surface portion 31 is desirable, since it tends to force the bow down and to swing the stern in the proper direction for the turn. A particularly desirable feature of the strakes is to reduce side slip on turns, and the portion 31, by keeping the bow down, tends to provide improved act-ion of the strakes along the waist 35.

While only a certain preferred embodiment of this invention has been shown and described by way of illustration, many modifications will occur to those skilled in the art and it is, therefore, desired that it be understood that it is intended in the appended claims to cover all such modifications as fall within the true spirit and scope of this invention.

What is claimed as new and what is desired to secure by Letters Patent of the United States is:

1. In a V bottom speedboat hull of the type having a first longitudinal strake disposed entirely above the level of compacted water during high speed operation, and a second longitudinal strake disposed inwardly and downwardly of said first strake and including an after portion which is below the water level at low speeds and which does not extend below the level of compacted water at high speeds, said strakes extending forwardly from the stern of said hull, said hull presenting a smooth hull surface between said strakes, a discontinuous outer hull surface portion disposed between said straltes fairing gradually from said hull surface at a distance from the stern equal to between about one-fifth to one-twentieth of the length dimension of said hull and extending aftwardly therefrom at an angle of between about two and six degrees outwardly in relation to said hull surface and rearwardly and terminating substantially at said stern, said discontinuous surface portion being at least substantially entirely below the water level during acceleration of the hull from low speeds and being substantially entirely out of compacted water during high speed straight ahead operation.

2. In a speedboat hull of the type having a stern transom and a V bottom with a smooth outer surface, the bottom being provided on each side of the keel with a lower strake adjacent the keel, an upper strake and at least one intermediate strake including a first intermediate strake occurring next to said upper strake, each said strake having a length greater than about one half of the water line length of the hull and extending longitudinally of the hull and each comprising a downwardly facing planing surface terminating outwardly in a respective strake edge and an outwardly facing generally upright surface extending upwardly from said edge, said hull bottom smooth surface occurring between said strakes with said strakes extending outwardly thereof and said strake surfaces fairing into said hull surface, said upper strake and said first intermediate strake extending to said transom, said hull being trimmed to submerge the after end of the hull to the depth at which said upper strake is substantially at water level when the hull is at rest and when it is being propelled at low speeds, said hull being adapted at high cruising and racing speeds to plane on the planing surfaces of said lower bottom strake and of at least one said intermediate strake with said upper strake and the outwardly facing surface of said first intermediate strake out of the water throughout their lengths, the improvement which comprises, on each respective side of the keel, a generally downwardly facing surface portion disposed between said upper and said one intermediate strake of the respective side, said surface portion meeting the smooth outer hull surface and the downwardly facing surface of said upper strake and smoothly fairing therefrom at a distance equal to approximately one-fifth to one-twentieth of the hull length dimension forward of the transom and said portion extending from said meeting aftwardly at a small angle to said hull surface to and terminating at said transom substantially even with said edges of the upper and first intermediate strakes, said portion being operative at low and medium planing speeds of the hull to provide substantial lift to the after end of the hull and being inoperative and above the water line during normal cruising and racing speed operation of the hull.

3. In a V bottom speedboat hull of the type having a hard chine disposed entirely above the level of compacted Water during high speed operation, and a second longitudinal strake disposed inwardly and downwardly of said chine and including an after portion which is below the water level at low speeds and which does not extend below the level of compacted water at high speeds, said strake and chine extending forwardly from the stern of said hull, said hull presenting a smooth hull surface between said strake and chine, a discontinuous outer hull surface portion disposed between said strake and chine fairing gradually from said hull surface at a distance from the stern equal to between about one-fifth to one-twentieth of the length dimension of said hull and extending aftwardly therefrom at an angle of between about two and six degrees outwardly in relation to said hull surface and rearwardly and terminating substantially at said stern, said discontinuous surface portion being at least substantially entirely below the water level during acceleration of the hull from low speeds and being substantially entirely out of compacted water during high speed straight ahead operation.

References Cited in the file of this patent UNITED STATES PATENTS Canazzi May 4, 1954 2,989,939 Tatter June 27, 1961 3,038,179 Wagemaker June 12, 1962 

1. IN A V BOTTOM SPEEDBOAT HULL OF THE TYPE HAVING A FIRST LONGITUDINAL STRAKE DISPOSED ENTIRELY ABOVE THE LEVEL OF COMPACTED WATER DURING HIGH SPEED OPERATION, AND A SECOND LONGITUDINAL STRAKE DISPOSED INWARDLY AND DOWNWARDLY OF SAID FIRST STRAKE AND INCLUDING AN AFTER PORTION WHICH IS BELOW THE WATER LEVEL AT LOW SPEEDS AND WHICH DOES NOT EXTEND BELOW THE LEVEL OF COMPACTED WATER AT HIGH SPEEDS, SAID STRAKES EXTENDING FORWARDLY FROM THE STERN OF SAID HULL, SAID HULL PRESENTING A SMOOTH HULL SURFACE BETWEEN SAID STRAKES, A DISCONTINUOUS OUTER HULL SURFACE PORTION DISPOSED BETWEEN SAID STRAKES FAIRING GRADUALLY FROM SAID HULL SURFACE AT A DISTANCE FROM THE STERN EQUAL TO BETWEEN ABOUT ONE-FIFTH TO ONE-TWENTIETH OF THE LENGTH DIMENSION OF SAID HULL AND EXTENDING AFTWARDLY THEREFROM AT AN ANGLE OF BETWEEN ABOUT TWO AND SIX DEGREES OUTWARDLY IN RELATION TO SAID HULL SURFACE AND REARWARDLY AND TERMINATING SUBSTANTIALLY AT SAID STERN, SAID DISCONTINUOUS SURFACE PORTION BEING AT LEAST SUBSTANTIALLY ENTIRELY BELOW THE WATER LEVEL DURING ACCELERATION OF THE HULL FROM LOW SPEEDS AND BEING SUBSTANTIALLY ENTIRELY OUT OF COMPACTED WATER DURING HIGH SPEED STRAIGHT AHEAD OPERATION. 